The document discusses aeration and types of aerators. Aeration is the process of absorbing oxygen from air or bringing water and air into close contact. There are two main categories of aerators: 1) air into water aerators that inject air bubbles into water and 2) water into air aerators that create small drops of water falling through air. Common types of aerators include gravity aerators like cascade and cone aerators, spray aerators, diffused air aeration systems, and mechanical aerators like surface and turbine aerators. Aeration serves important functions like mixing, keeping solids in suspension, and supplying oxygen for biochemical reactions in wastewater treatment.

1. WELCOME

2. Aeration and Types of Aerators
Presented by
Kari Venkata Sai
2016-18-015

3. Aeration
The process of absorbing oxygen from air is known
as aeration.
(or)
The process of bringing water and air into close
contact in order to remove dissolved gases, such as
carbon dioxide, and to oxidize dissolved metals such
as iron.
It can also be used to remove volatile organic
chemicals (VOC) in the water.

4. Aeration serves three important functions :
1. Mixing the returned sludge with effluent from
primary treatment.
2. Keeping the activated sludge in suspension.
3. Supplying the oxygen to the biochemical
reactions necessary for the stabilization of the
wastewater

5. Why we use Aeration?
Oxidation of organic matter.
To increase dissolved oxygen content.
To reduce the concentration of taste and odor causing
substances, such as hydrogen sulfide and various
organic compounds, by volatilization/stripping or
oxidation.
To oxidize iron and manganese, rendering them
insoluble.

6. Aerators generally falls into two categories
1. Air into Water – This method creates small bubbles
of air that are injected into the water stream.
2. Water into Air – This method is designed to produce
small drops of water that fall through air.
3. All aerators are designed to create a greater amount
of contact between the air and water to enhance the
transfer of gases.

7. Aerators
Gravity aerators
Cascade aerator Cone aerator
Spray aerators Diffused air
aeration system
Mechanical
aerators
Types of Aerators

8. Gravity Aerators
1. Cascade aerators
 A cascade aerator consists
of a series of steps that
the water flows over. In
all cascade aerators,
aeration is accomplished
in the splash zones.
 Cascade aerators can be
used to oxidize iron and
to partially reduce
dissolved gases.

9. 2. Cone aerators
 Cone aerators are used
primarily to oxidize iron
and manganese from the
ferrous state to the ferric
state prior to filtration.
The water being pumped
to the top of the cones
and then being allowed to
cascade down through
the aerator.

10. Spray aerators
 This type of aerator has one or more spray nozzles connected
to a pipe manifold.
 The water is sprinkled in fine jets through nozzles to a height
of about 2 m to 2.5 m.
 The nozzles are generally operated at a pressure of 0.07 to
0.14 N/mm2.
 The discharge through nozzle will depend upon its design and
available head of water.

11. Diffused air aeration system
 The perforated pipes are installed at the bottom of
tanks. The compressed air is blown through these
pipes.
 The air bubbles while coming up from the bottom of
tank come into close contact of water contained in the
tank and aeration of water is thus achieved.
 The depth of aeration tanks is generally about 2.5 m to
3 m and they generally work on the principle of
continuous flow with minimum detention period of 15
minutes.
 The quantity of air consumed per 1000 litres of water
varies from 0.3 m3 to 0.6 m3.

13. Mechanical aerators
Mechanical aerators are of two general types; surface aerators and
turbine aerators.
Surface aerators consist of submerged or partially submerged
impellers, which are centrally mounted in the aeration tank.
Surface aerators agitate the wastewater vigorously, entraining
air in the wastewater and causing a rapid change of the air-
water interface to facilitate solution of the air.
Turbine aerators are usually up flow types that rely on violent
agitation of the surface and air entrainment for their efficiency.
A draft tube may be utilized to control the flow pattern of the
circulating liquid within the aeration tank. The draft tube is a
cylinder with flared ends mounted concentrically with the
impeller, and extending from just above the floor of the
aeration tank to just beneath the impeller.

14. Mechanical Aerators types

15. DIFFUSED AERATION MECHANICAL AERATION
1. Superior Mixing
• full mixing for any depth
• full basin utilization
• Limited mixing depth
• Limited energy location- poor distribution
2. Major Energy Saving
• Approx 40% energy saving
• Low energy demand
• High energy cost
• High energy demand
3. Possible Flexibility
• Can turn down or throttle entire system • Loss of air when unit are turn off
• No throttling possible
4. Capital Cost
• If used in deep basin very economical
• Short payback period
• If used in deep basin very costly
• Comparatively high payback period.

16. Common operating problems
 Super saturation.
 Slow removal of the hydrogen sulfide.
 Algae production.
 Clogged filters.
 Overuse of energy.